Set to low (SLAVE)
SPIx CLK
_
SPIx SIMO
_
SPIx SOMI
_
SPIx_ENA
Write to SPIDAT1 (MASTER)
SPIx_SCS[n]
SPIx CLK
_
SPIx SOMI
_
SPIx SIMO
_
Slave
(MASTER = 0; CLKMOD = 0)
SPIx CLK
_
SPIx SOMI
_
SPIx_SIMO
Master
(MASTER = 1; CLKMOD = 1)
SPIBUF
SPIDAT1
CPU/DMA
write
CPU/DMA
read
SPIDAT1
SPIBUF
CPU/DMA
read
CPU/DMA
write
SPIx_ENA
SPIx_ENA
SPIx SCS[n]
_
SPIx_SCS[n]
Architecture
1426
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Serial Peripheral Interface (SPI)
Figure 29-5. SPI 5-Pin Option with SPIx_ENA and SPIx_SCS[n]
NOTE:
Push-Pull mode of the SPIx_ENA pin can be used only when there is a single slave in the
system. When there are multiple SPI slave devices connected to the common SPIx_ENA
pin, all the slaves should configure their SPIx_ENA pins in high-impedance mode.
During an SPI transfer, if slave mode SPI detects a deassertion of its chip select even before
its internal character length counter overflows, then it 3-states its SPIx_SOMI and SPIx_ENA
(if SPIINT0.ENABLEHIGHZ bit is set to 1) pins. Once this condition has occurred, if a
SPIx_CLK edge is detected while the chip select is deasserted, then the SPI stops that
transfer and sets an error flag DLENERR (data length) and generates an interrupt if enabled.